Element Ti and Zr Influence TZM Alloy (2)

After adding elements Ti and Zr TZM alloy grain is fine, and there are a lot of second-phase grains and pore between Mo grains. The study found that TZM second phase grains and pore for TZM alloy has some inhibiting effect. Grain boundaries provide resistance to deformation of the material, with the grain refinement, polycrystalline strength improved. Despite the added TiH2 and ZrH2 of TZM alloy pores more, the relative density is low, and there is plenty of space particles, but due to finer grain, so the strength of TZM is higher.

However, the second phase particles and pores with grains Mo interface is easy to become a source of micro-cracks to reduce the fracture toughness of the material, thereby causing material happen intergranular brittle fracture. Wherein when the size of the pores and the second phase particles become smaller, more dispersed distribution, strengthening the effect is more obvious. Conversely, when a large particle size when the second phase, it will affect the properties of the alloy.

Element Ti and Zr Influence TZM Alloy (1)

Study found that the addition elements Ti and Zr will make TZM alloy density slightly less than molybdenum sintered body’s. This is due to the elements Ti and Zr are added in the form TiH2 and ZrH2, when sintered at 400 ~ 800 ℃ condition, the TiH2 and ZrH2 after dehydrogenation to generate hydrogen to increase the porosity of the material slightly. Although Ti and Zr slightly reduced the density of the TZM alloy’s sintered body, but refines the grain size of the sintered body. Mo grain size is generally between 10~20um and there are no second phase particles between grains, fewer voids. TZM alloy which added TiH2 and ZrH2 the grain size generally between 5~15um, comparing to molybdenum is small. Meanwhile, Mo grains which exist a large number of second-phase particles and pores and there are a large number of spherical particles and spherical pits. What’s more there is distribution uniformly.

By analyzing the TZM alloy spherical particles found that these particles are (Mo, Ti, Zr) xOy compound composite by Mo, Ti, Zr and O elements. (Mo, Ti, Zr) xOy alloy particles in favor of oxygen purification, generation of dislocation pinning effect, but, to refine the grain, thus contributing to improve the alloy strength.